title: Oral clopidogrel improves cutaneous microvascular function through EDHF-dependent mechanisms in middle-aged humans.
abstract: Platelet P₂Y₁₂-ADP and COX-1 receptor inhibition with oral clopidogrel (CLO) and low-dose aspirin (ASA), respectively, attenuates reflex-mediated cutaneous vasodilation, but little is known about how these medications affect local vasodilatory signaling. Reactive hyperemia (RH) results in vasodilation that is mediated by sensory nerves and endothelium-derived hyperpolarization factors (EDHF) through large-conductance calcium-activated potassium channels, whereas slow local heating (LH) elicits vasodilation largely through the production of nitric oxide (NO). We hypothesized that CLO and ASA would attenuate locally mediated cutaneous vasodilation assessed by RH and LH (0.5°C/min). In a randomized, cross-over, double-blind placebo-controlled study, nine healthy men and women (56 ± 1 yr) took CLO (75 mg), ASA (81 mg), and placebo for 7 days. Skin blood flow was measured (laser-Doppler flowmetry, LDF) and cutaneous vascular conductance (CVC) was calculated (LDF/mean arterial pressure) and normalized to maximal CVC (%CVCmax: 43°C and 28 mM sodium nitroprusside). RH response parameters, including area under the curve (AUC), total hyperemic response (THR), and the decay constant tau (λ) were calculated. NO-dependent vasodilation during LH was assessed by calculating the difference in %CVCmax between a control site and an NO synthase-inhibited site (10 mM l-NAME: intradermal microdialysis). CLO augmented the AUC and THR (AUCclo = 3,783 ± 342; THRclo = 2,306 ± 266% CVCmax/s) of the RH response compared with ASA (AUCASA = 3,101 ± 325; THRASA = 1,695 ± 197% CVCmax/s) and placebo (AUCPlacebo = 3,000 ± 283; THRPlacebo = 1,675 ± 170% CVCmax/s; all P < 0.0001 vs. CLO). There was no difference in the LH response or calculated NO-dependent vasodilation among treatments (all P > 0.05). Oral CLO treatment augments vasodilation during RH but not LH, suggesting that CLO may improve cutaneous microvascular function.
authors.affiliation: Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania.
authors.forename: Jessica D
authors.initials: JD
authors.lastname: Dahmus
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Bruning
authors.forename: W Larry
authors.initials: WL
authors.lastname: Kenney
authors.forename: Lacy M
authors.initials: LM
authors.lastname: Alexander
mesh_terms: D000284:Administration, Oral; D000704:Analysis of Variance; D001241:Aspirin / Q000008:administration & dosage; D001685:Biological Factors / Q000378:metabolism*; D001783:Blood Flow Velocity / Q000187:drug effects; D000077144:Clopidogrel; D018592:Cross-Over Studies; D016861:Cyclooxygenase Inhibitors / Q000008:administration & dosage; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D006940:Hyperemia / Q000503:physiopathology; D017078:Laser-Doppler Flowmetry; D008297:Male; D008833:Microcirculation / Q000187:drug effects*; D017551:Microdialysis; D055806:Microvessels / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D008875:Middle Aged; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000008:administration & dosage; D010414:Pennsylvania; D058921:Purinergic P2Y Receptor Antagonists / Q000008:administration & dosage*; D012039:Regional Blood Flow / Q000187:drug effects; D012867:Skin / Q000098:blood supply*; D012881:Skin Temperature; D013988:Ticlopidine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D013997:Time Factors; D014664:Vasodilation / Q000187:drug effects*
chemical_list: D001685:Biological Factors; D016861:Cyclooxygenase Inhibitors; D020030:Nitric Oxide Donors; D058921:Purinergic P2Y Receptor Antagonists; C067410:endothelium-dependent hyperpolarization factor; D009569:Nitric Oxide; D000077144:Clopidogrel; D013988:Ticlopidine; D001241:Aspirin
keywords: Plavix, local heating; aspirin; reactive hyperemia; skin blood flow